Answer:
Reference angle:
is not defined.
Step-by-step explanation:
The angle
goes from the positive x-axis to the negative y-axis.
Therefore the reference angle can be calculated as following:

We know that
is:

If
then
, therefore
is not defined, because the division by 0 is not defined.
Answer:
=-18x^2+78xy-24y^2
Step-by-step explanation:
(-2x+8y)(9x-3y)
-18x^2+6xy+72yx-24y^2
-18x^2+(6xy+72xy)-24y^2
=18x^2+78xy-24y^2
Answer:
-300
Step-by-step explanation:
200-500=-300
500+(-300)=200
This is the associative property of addition